Minimally invasive unicompartmental knee arthroplasty for spontaneous osteonecrosis of the knee joint

Abstract

Objective To explore the outcome and surgical technique of minimally invasive unicompartmental knee arthroplasty (UKA) for spontaneous osteonecrosis of the knee joint.Methods From January 2009 to June 2013,twenty-seven cases with medial compartmental spontaneous osteonecrosis treated by minimally invasive Oxford phase 3 UKA were reviewed retrospectively.Twelve knees were male and 15 were female,with an average age of 64.6±8.6 years (52-82 years).At the time of diagnosis,11 patients presented with grade Ⅲ necrosis,and 16 grade Ⅳ,following Mont's classification.The pain,range of motion (ROM) and HSS score of the knees were evaluated before and after UKA.Pre-and post-operative alignment of the low limbs were measured and compared respectively.According to the guidelines proposed by the Oxford group,postoperative radiographic assessments were made at the final follow-up.Results All of the patients were followed up for a mean time of 27.8± 15.9 months (6-59months).There were no serious adverse events such as infection,bearing dislocation,aseptic loosening,pulmonary embolism,deep venous thrombosis,cardio-cerebral vascular incident or psychogenia.There was 1 revision from unrelated causes (fracture of tibia plateau) at 3 years after arthroplasty.One femoral component was tilted with postoperative radiographic angle ＞ 10°.One radiolucent line was observed in the SONK series.There were no clinical symptoms of the two implant failures at the last follow up.VAS score was reduced from 6.9±0.9 to 2.0±1.1 (t=19.27,P=0.00).96.3％ (26/27) of pain was relieved.The mean post-operative ROM and femorotibial angle were 125.7°±9.6°,177.7°±3.1°,respectively.HSS score was increased from 61.3±9.7 to 93.0±4.8 (t=14.46,P=0.00).Of the patients,96.3％ (26/27) were satisfied with the outcome of this surgical procedure.Conclusion Minimally invasive UKA is an effective method for spontaneous osteonecrosis of the knee with fewer traumas and fast recovery.The early term outcome of UKA is encouraging. Key words: Arthroplasty, replacement, knee; Knee joint; Osteonecrosis